抄録
Clonidine or Catapres at a dose of 5μg/Kg was administered intravenously to spontaneously hypertensive rats (SHR) at 16 weeks of age under pentobarbital anesthesia. The mean arterial pressure was lowered from 138±4mm Hg (mean±SEM, n=6) to 100±5 and the heart rate from 350±9/min to 299±14. The mean discharge rate of vasoconstrictor fibers of the splanchnic nerve estimated by cutting and stimulating the nerve was 0.33±0.09/sec for the right splanchnic nerve and 0.90±0.27/sec for the left splanchnic nerve (after severance of the right nerve). These values were significantly (P<0.005 and 0.001, respectively) lower than the corresponding values in untreated SHR and comparable with those in normotensive control rats. The concomitant decrease in arterial pressure and sympathetic discharge rate confirms that the major contribution to hypertension of SHR is by elevation of the sympathetic tone.
